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Diffstat (limited to 'crypto/ext4crypt/ext4_crypt.cpp')
| -rw-r--r-- | crypto/ext4crypt/ext4_crypt.cpp | 180 |
1 files changed, 180 insertions, 0 deletions
diff --git a/crypto/ext4crypt/ext4_crypt.cpp b/crypto/ext4crypt/ext4_crypt.cpp new file mode 100644 index 000000000..029db7567 --- /dev/null +++ b/crypto/ext4crypt/ext4_crypt.cpp @@ -0,0 +1,180 @@ +/* + * Copyright (C) 2015 The Android Open Source Project + * + * Licensed under the Apache License, Version 2.0 (the "License"); + * you may not use this file except in compliance with the License. + * You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +/* TWRP NOTE: Kanged from system/extras/ext4_utils/ext4_crypt.cpp + * because policy_to_hex, e4crypt_policy_set, and e4crypt_policy_get + * are not exposed to be used. There was also a bug in e4crypt_policy_get + * that may or may not be fixed in the user's local repo: + * https://android.googlesource.com/platform/system/extras/+/30b93dd5715abcabd621235733733c0503f9c552 + */ + +#include "ext4_crypt.h" + +#include <dirent.h> +#include <errno.h> +#include <string.h> +#include <unistd.h> + +#include <fcntl.h> +#include <asm/ioctl.h> +#include <sys/syscall.h> +#include <sys/stat.h> +#include <sys/types.h> + +#include <android-base/file.h> +#include <android-base/logging.h> +#include <cutils/properties.h> + +#define XATTR_NAME_ENCRYPTION_POLICY "encryption.policy" +#define EXT4_KEYREF_DELIMITER ((char)'.') + +// ext4enc:TODO Include structure from somewhere sensible +// MUST be in sync with ext4_crypto.c in kernel +#define EXT4_KEY_DESCRIPTOR_SIZE 8 +#define EXT4_KEY_DESCRIPTOR_SIZE_HEX 17 + +struct ext4_encryption_policy { + char version; + char contents_encryption_mode; + char filenames_encryption_mode; + char flags; + char master_key_descriptor[EXT4_KEY_DESCRIPTOR_SIZE]; +} __attribute__((__packed__)); + +#define EXT4_ENCRYPTION_MODE_AES_256_XTS 1 +#define EXT4_ENCRYPTION_MODE_AES_256_CTS 4 +#define EXT4_ENCRYPTION_MODE_PRIVATE 127 + +static int encryption_mode = EXT4_ENCRYPTION_MODE_PRIVATE; + +// ext4enc:TODO Get value from somewhere sensible +#define EXT4_IOC_SET_ENCRYPTION_POLICY _IOR('f', 19, struct ext4_encryption_policy) +#define EXT4_IOC_GET_ENCRYPTION_POLICY _IOW('f', 21, struct ext4_encryption_policy) + +#define HEX_LOOKUP "0123456789abcdef" + +extern "C" void policy_to_hex(const char* policy, char* hex) { + for (size_t i = 0, j = 0; i < EXT4_KEY_DESCRIPTOR_SIZE; i++) { + hex[j++] = HEX_LOOKUP[(policy[i] & 0xF0) >> 4]; + hex[j++] = HEX_LOOKUP[policy[i] & 0x0F]; + } + hex[EXT4_KEY_DESCRIPTOR_SIZE_HEX - 1] = '\0'; +} + +extern "C" bool e4crypt_policy_set(const char *directory, const char *policy, + size_t policy_length, int contents_encryption_mode) { + if (contents_encryption_mode == 0) + contents_encryption_mode = encryption_mode; + if (policy_length != EXT4_KEY_DESCRIPTOR_SIZE) { + printf("policy wrong length\n"); + LOG(ERROR) << "Policy wrong length: " << policy_length; + return false; + } + int fd = open(directory, O_DIRECTORY | O_NOFOLLOW | O_CLOEXEC); + if (fd == -1) { + printf("failed to open %s\n", directory); + PLOG(ERROR) << "Failed to open directory " << directory; + return false; + } + + ext4_encryption_policy eep; + eep.version = 0; + eep.contents_encryption_mode = contents_encryption_mode; + eep.filenames_encryption_mode = EXT4_ENCRYPTION_MODE_AES_256_CTS; + eep.flags = 0; + memcpy(eep.master_key_descriptor, policy, EXT4_KEY_DESCRIPTOR_SIZE); + if (ioctl(fd, EXT4_IOC_SET_ENCRYPTION_POLICY, &eep)) { + printf("failed to set policy for '%s' '%s'\n", directory, policy); + PLOG(ERROR) << "Failed to set encryption policy for " << directory; + close(fd); + return false; + } + close(fd); + + char policy_hex[EXT4_KEY_DESCRIPTOR_SIZE_HEX]; + policy_to_hex(policy, policy_hex); + LOG(INFO) << "Policy for " << directory << " set to " << policy_hex; + return true; +} + +extern "C" bool e4crypt_policy_get(const char *directory, char *policy, + size_t policy_length, int contents_encryption_mode) { + if (contents_encryption_mode == 0) + contents_encryption_mode = encryption_mode; + if (policy_length != EXT4_KEY_DESCRIPTOR_SIZE) { + LOG(ERROR) << "Policy wrong length: " << policy_length; + return false; + } + + int fd = open(directory, O_DIRECTORY | O_NOFOLLOW | O_CLOEXEC); + if (fd == -1) { + PLOG(ERROR) << "Failed to open directory " << directory; + return false; + } + + ext4_encryption_policy eep; + memset(&eep, 0, sizeof(ext4_encryption_policy)); + if (ioctl(fd, EXT4_IOC_GET_ENCRYPTION_POLICY, &eep) != 0) { + PLOG(ERROR) << "Failed to get encryption policy for " << directory; + close(fd); + return false; + } + close(fd); + + if ((eep.version != 0) + || (eep.contents_encryption_mode != contents_encryption_mode) + || (eep.filenames_encryption_mode != EXT4_ENCRYPTION_MODE_AES_256_CTS) + || (eep.flags != 0)) { + LOG(ERROR) << "Failed to find matching encryption policy for " << directory; + return false; + } + memcpy(policy, eep.master_key_descriptor, EXT4_KEY_DESCRIPTOR_SIZE); + + return true; +} + +extern "C" bool e4crypt_set_mode() { + const char* mode_file = "/data/unencrypted/mode"; + struct stat st; + if (stat(mode_file, &st) != 0 || st.st_size <= 0) { + printf("Invalid encryption mode file %s\n", mode_file); + return false; + } + size_t mode_size = st.st_size; + char contents_encryption_mode[mode_size + 1]; + memset((void*)contents_encryption_mode, 0, mode_size + 1); + int fd = open(mode_file, O_RDONLY); + if (fd < 0) { + printf("error opening '%s': %s\n", mode_file, strerror(errno)); + return false; + } + if (read(fd, contents_encryption_mode, mode_size) != mode_size) { + printf("read error on '%s': %s\n", mode_file, strerror(errno)); + close(fd); + return false; + } + close(fd); + if (!strcmp(contents_encryption_mode, "software")) { + encryption_mode = EXT4_ENCRYPTION_MODE_AES_256_XTS; + } else if (!strcmp(contents_encryption_mode, "ice")) { + encryption_mode = EXT4_ENCRYPTION_MODE_PRIVATE; + } else { + printf("Invalid encryption mode '%s'\n", contents_encryption_mode); + return false; + } + printf("set encryption mode to %i\n", encryption_mode); + return true; +} |